Diesel fuel



Patented Oct. 31, 1939 UNITED STATES PA ENT OFFICE mEsEL rum.

tion of New York Na Drawing. Application mm 14, 1937,

Serial No. 168,900

Claims.

, This invention has to do in a general way with fuels for internal combustion engines of the Diesel type'and is more particularly concerned with the modification of such fuels by the addition of characterizing ingredients for the purpose of modifying or controlling the combustion characteristics.

In the Diesel cycle internal combustion engine, where the fuel is injected into a combustion space, it is important to the attainment of maximum efficiency that the delay period between injection and ignition be short. It will thus be seen that enhanced speed of ignition is a characteristic that is highly desirable. Improperly delayed ignition in a Diesel engine gives rise to the phenomenon known as knocking, due to improper coordination of combustion and cylinder conditions. By accelerating the ignition point of Diesel fuel it is possible to lower the compression pressure, which will insure spontaneous ignition without combustion shock, thereby increasing the ease of starting and smoothness with which combustion takes place. In this same connection, the low compression pressure permits of a lower weight in the engine and a lower cost per given power output.

It has been found that the ignition quality of a fuel oil can be improved by the addition of small amounts of certain compounds which'act as ignition. accelerators. This offers a means for improving the better grades of Diesel fuels and a means of Widening the range of available fuels by raising the ignition quality of lower grades to a point where they can be satisfactorily used.

A number of compounds have been proposed asignition accelerators for Diesel fuels. Among these compounds are such materials as ethyl nitrate, amyl nitrite, and certain aldehydes and peroxides.

Many of these compounds are unsatisfactory from the standpoint of stability, cost, toxicity, or because of their tendency to form corrosive gases in the combustion chamber of the engine.

Our present invention is directed to Diesel type fuels which have been improved in ignition quality by the addition of novel compounds which promote rapidity of combustion and so give the desired control to the combustion characteristics of the fuel.

- By the term Diesel type fuels or Diesel fuel as it is used herein we have reference not only to the distillates of the kerosene-like boiling range commonly denoted as Diesel fuel, but we intend to include as well the general field of hydrocarbon products, both heavier and lighter than the fuel above referred to, such for example as the light and heavy fuel oils and gasoline for use in Diesel cycle engines.

This invention is predicated upon the discovery that organic compounds which may be characterized by the general type formula,

in which R and R represent alkyl radicals, can be used as additive ingredients for Diesel fuel to' accelerate the ignition quality of such fuels, or decrease the ignition delay period."

Organic compounds of the general type contemplated by this invention can, for example, be synthesized by reacting sulfur monochloride with secondary alkyl amines.

As an example of an additive ingredient of the general type contemplated by this invention and a method of its preparation, we have prepared diamyl amine disulfide or his (diamyl amine) disulfide by the interaction of sulfur monochloride (S2Cl2) and diamyl amine. The reaction in which the bis (diamyl amine) disulfide is formed probably takes place according to the following equation:

Disulfides of the general type obtained according to the above reaction may be broadly defined R2NSS-NR2 in which R represents an alkyl group. It is not I our intention to limit the scope of our present invention to a particular type formula, however,

and in its broader aspect our invention contemplates as an additive ingredient for Diesel fuels those sulfur-nitrogen organic compounds of the type which -may be synthesized by reacting a secondary alkyl amine with a sulfur monohalide.

In carrying out the synthesis represented by the equation above, which illustrates the preparation of compounds of the type contemplated by this invention, 4 moles (628 gms.) of diamyl amine and 800 cc. of benzene were placed in a reaction container. One moi (135 gms.) of sulfur monochloride was diluted with 200 cc. of himacne, and this solution gradually added to the diamylamine solution. It will be observed that two equivalents of amine were employed, since two moles were concentrated in forming the hydrochloride solution, which is apparently unreactive with the sulfur monochloride. After the sulfur monochloride had been added, the mixture was cooled and stirred until the heat of reaction had dissipated, after which the hydrochloride salt of the amine was filtered off. The benzene in the filtrate was removed by distillation and any unreacted amine was removed by distilling under reduced pressure.

In conducting the tests with which we have demonstrated the value of compounds belonging to the general class contemplated by this invention as ingredients for decreasing the ignition delay periods of Diesel fuels, we have determined the ignition quality of Diesel fuels blended with material of this general character by comparison with standard reference fuels in a converted C. F. R. engine, using the ignition delay method. The results of these tests are expressed by eetane numbers. The cetane number is the per cent by volume of cetane in a blend of cetane and alpha-methyl naphthalene, which blended fuel has the same combustion characteristics as the sample being tested. (Proc. Am. Soc. Testing Material vol. 36, I p. 418.) An increase in cetane number indicates a decrease in delay between fuel injection and fuel ignition, and consequently indicates an improvement in fuel combustion characteristics.

The particular material used in conducting these tests was the his (diamyl amine) disulflde prepared according to the foregoing procedure, and as examples of the improved ignition quality of the fuel when blended with this material we have indicated in the following table the results of a plurality of tests in which the improved cetane numbers derived through various percentages of added ingredients were obtained. The base fuel stock used in these tests was a petroleum distillate commonly known as Number Two Fuel .011, having a flash point of 156 F., specific gravity of 0.86, and a Lovibond color of 0.25. The cetane number of the unblended stock was 42.0 and it is clearly apparent from the table that compounds of the type prepared by the reaction of an amine with a sulfur halide effect a material increase in cetane number.

Organic compounds of the type exemplified above, which it will be observed contain the sulfur-nitrogen linkage (=NSSN=) maybe used in amounts varying with the base fuel stock and the extent to which it is desired to improve its ignition quality. For example, compounds of this character may be used in proportions up to about 5.0% of the fuel, but in general lower concentrations are preferred, and a concentration in the neighborhood of 1.0% is believed to be sufficient for most purposes.

In the foregoing description and in the following claims the terms Diesel fuel", hydrocarbon fuel oil, etc., include any and all types of hydrocarbon products intended for use in any engine operating according to the Diesel cycle.

We claim:

1. An improved Diesel fuel comprising: hydrocarbon fuel oil and in admixture therewith a minor proportion of his (diamylamine) disulfide in sufficient amount to decrease the ignition delay period of the fuel.

2. An improved Diesel fuel comprising: hydrocarbon fuel oil and in admixture therewith a minor proportion of his (dialkylamine) disulfide in suflicient amount to decrease the ignition delay period of the fuel.

3. An improved Diesel fuel having in admixture therewith a minor proportion of a compound having the proboble formula in which R represents an alkyl group.

4. The method of accelerating the ignition of fuels for internal combustion engines wherein fuel ignition is effected by compression of fuel and air in the cylinder which comprises providing the fuel-air mixture prior to ignition with a minor proportion of his (dialkylamine) disulfide in an amount suflicient to decrease the ignition delay period of the fuel mixture.

5. The method of accelerating the ignition of fuels for internal combustion engines wherein fuel ignition is effected by compression of fuel and air in the cylinder which comprises providing the fuel-air mixture prior to ignition with a minor proportion of bis (diamylamine) disulfide in an amount sufficient to decrease the ignition delay period of the fuel mixture.

WILLIAM H. JAMES. ROBERT C. MORAN. EDWIN M. NYGAARD. 

